Should Filter Paper Be Wet? What Impact Does Dry Filter Paper Have on Pour-Over Coffee? Why Use Twice as Much Water for Blooming?

Last month, FrontStreet Coffee compared wetting versus not wetting filter paper. Detail-loving readers caught a key point in that article: an unwetted filter paper absorbs coffee liquid during the brew. But the brief mention left questions unanswered, and they wrote in: Do different filter papers absorb the same amount of liquid? And what does losing that portion of coffee actually do to the final taste?

Experimental Design

Since you asked so sincerely, FrontStreet Coffee ran an experiment. We used two drippers — the V60 and the Origami — one with cone-shaped paper, the other with flat-bottom paper, forming two separate groups. Would wetted versus unwetted paper change liquid volume, concentration, or taste? (The filter paper used carried no off-flavors or other unwanted properties.)

The Brewing Experiment

The beans were Finca Limonera — Ombligo, cupping with blackcurrant, blueberry, and sweet orange. Dose: 15g of coffee at a 1:15 coffee-to-water ratio, 92°C water, ground to 9.5 on the EK43 (fine-sugar consistency), brewed with a three-pour method. Let's begin! (Brewing process omitted.)

Results

Because both drippers have ribbing, brew times between wetted and unwetted paper differed by only about 7 seconds, with the wetted paper finishing slightly slower (V60 at 2:06, Origami at 2:12). Now, the liquid weights. We poured a precise 225ml of hot water, and whether with the V60's cone paper or the Origami's flat-bottom paper, the wetted-paper brews yielded about 190ml of liquid while the unwetted-paper brews yielded about 184ml.

(V60 group)

(Origami group)

Accounting for the 30ml of hot water absorbed by the coffee grounds themselves, the filter paper took up only about 5ml of coffee liquid. So what does that 5ml do to concentration and taste? Over to the concentration meter — and our tasting panel — for separate evaluation.

(V60 group)

(Origami group)

Analysis and Conclusion

Settling for differences caused by pour technique, the concentration meter showed no significant gap between the pairs. Our tasters likewise found almost no difference among the four cups (within their respective groups). Conclusion: the coffee absorbed by an unwetted filter paper has little effect on the final cup. The reason lies in which coffee the paper absorbs first. When the paper is dry, it saturates itself with the very first liquid it touches — and that first portion of liquid is typically the weakest of the whole brew.

Why? Remember that blooming exists to pre-release carbon dioxide from the grounds so later pours can extract aromatics more effectively. The water poured during the bloom meets grounds that haven't degassed yet, so it can't extract aromatics as efficiently as subsequent pours — a lower extraction rate, and therefore a weaker concentration. That's exactly why we try to bloom with the minimum water needed, minimizing "wasted" hot water.

Conveniently, dry coffee grounds absorb water themselves, so we bloom with the amount the grounds can soak up — twice the weight of the dose — which minimizes waste, even though the grounds won't absorb every drop. The liquid an unwetted filter paper first meets is precisely that unabsorbed surplus. Having passed through grounds that weren't fully degassed, it carries little coffee substance. Missing it barely moves the overall taste (there's an effect on flavor, but truly minimal).

For the other effects of wetting versus not wetting filter paper, FrontStreet Coffee covered them in detail in the previous article, so we won't repeat them here.

FrontStreet Coffee Recommendation

A dry filter paper steals only the weakest few milliliters — but the dripper you choose shapes far more of the cup. The V60 remains the go-to recommendation for newcomers: its 60° cone and single large outlet let water flow to the center unimpeded, so the brew's speed and extraction depend on the pourer's control — ideal for the bright, aromatic coffees of the third wave. Three picks that shine in a V60:

FrontStreet Yirgacheffe Idido: The first stop for many into specialty coffee — vivid citrus, berries, and florals with a green-tea-like finish. Its acidity is soft and bright rather than sharp, making it an easy first pour-over.

FrontStreet Ethiopia Guji (Hua Kui): One of the most successful stars of recent years: intense tropical fruit — strawberry, passion fruit, jackfruit, even lychee — with obvious sweetness and almost no bitterness, so juicy it's been called "the least coffee-like coffee."

FrontStreet Kenya Cherry Tomato: From Thika at 1550–1750 meters, SL28 and SL34 given Kenya's 72-hour double-washed fermentation and a light roast. Dried cherry tomato and florals in the nose; bright, solid acidity like fresh-squeezed juice; snow pear and black plum through the middle; a clean finish of yellow sugar and green tea.